406 
GEOLOGY OF THE FOURTH DISTRICT. 
first named, with several on the east of them, unite in one general outlet, the Oswego river,, 
and empty their waters into Lake Ontario. All these lakes, with the exception of the Cayuga, 
are situated on the south of the great Helderberg series of limestones, which extend westward 
from the Hudson river. The northern extremity of Cayuga lake valley is excavated in this 
limestone, and in the Onondaga salt group below- The greater part of these excavations have 
been made in the rocks of the Hamilton group, the Portage group, and the northern portion 
of the Chemung group. The small western lakes of this series do not extend so low as the 
Hamilton group, as will be seen on reference to the Geological map of the district. 
These bodies of fresh water exert a very sensible influence upon the temperature of the 
surrounding country, and the effects of frosts upon vegetation bordering them is not observed 
so soon by many days as on the higher grounds. 
Cayuga lake, the most easterly of the chain, is nearly forty miles long, with an average 
breadth of more than two miles. Its greatest ascertained depth is ,390 feet. For several 
miles before reaching its northern extremity, this lake is quite shallow, the bottom being dis¬ 
tinctly visible ; finally it is covered by aquatic plants, which reach the surface, and these 
are succeeded by marsh grasses. The marshes have been before alluded to, and from their 
immense extent are of great interest. The mode of reclaiming these by dykes, and by re¬ 
moving the surplus water by aid of windmills, has been suggested in my annual reports, and 
it still appears to me practicable. Even during the warm summer months, there is almost 
constantly a sufficient breeze upon these lakes to move a windmill; and after the first expense 
of draining the surplus water from the higher grounds, it could be kept out by this method 
with little trouble or expense. 
Seneca lake, the second in order, is of about the same length and breadth as Cayuga. Its 
depth, however, is considerably greater, being five hundred and thirty feet. It does not become 
shallow toward the northern end, as Cayuga lake. The outlet of this lake is evidently of more 
recent excavation than that of the lake valley: it turns to the eastward, and joins Cayuga lake 
near its northern extremity. It cuts its channel through the Corniferous limestone, and the 
limestones and marls of the gypseous formation below. 
The channels of both these lakes are very similar, and their valleys extend northward, 
joining the great valley of the Susquehannah. Their banks are mostly perpendicular cliffs 
of shale and sandstone, for a height of ten to sixty feet; and from this the country rises in a 
gentle slope to a height of several hundred feet. This is covered with forest in its native state, 
and when cultivated, forms some of the most beautiful tracts. The surface is indented with 
ravines, which become deeper on approaching the lake shore, and open as deep gorges in 
its perpendicular cliffs on the margin. 
Crooked lake, is the third in the series. The aboriginal name of this lake is Keuka. Its 
northern half consists of two branches, separated by a bluff of land, which rises, at its southern 
extremity, more than three hundred feet above the lake. It appears to lie in a deepened por¬ 
tion of a north and south valley, which northward joins the valley of Flint creek, and south¬ 
ward the Conhocton at Bath. Its depth has been variously estimated; but from soundings 
made at several points, the average is probably less than two hundred feet. The outlet is 
